Tommy Caldwell and Kevin Jorgeson became the first to free-climb the rock formation’s Dawn Wall, a feat that many had considered impossible. They used ropes and safety harnesses to catch themselves in case of a fall, but relied entirely on their own strength and dexterity to ascend by grasping cracks as thin as razor blades and as small as dimes.

Two climbers vying to finish the once-seemingly impossible challenge of scaling a sheer slab of granite in California’s Yosemite National Park without climbing aids are closing in on the top of the 3,000-foot peak.

The 32-year-old has pleaded not guilty to a four-count indictment stemming from last year’s Rim Fire, which burned 400 square miles of the Sequoia National Forest, including parts of Yosemite National Park.